High-frequency dielectric waveguide coupling



Nov. 11, 1952: lAMs 2,617,880

HIGH-FREQUENCY DIELECTRIC WAVEGUIDE COUPLING Fi led Feb. 27, 1948 INVENTOR Jams ATTORNEY Patented Nov. 11, 1952 UNITED "STATES ATENT orFicE .HIGHwFREQUENCY DIELECTRIC 'WAVEGUIDE COUPLING Harley Iams, Venice, Calif., assignor to Radio Corporation of America, a corporationof Dela- 12 Claims. 1

This invention relates to radio frequency net- 'works'and moreparticularly'to networks wherein radio "energy is guided by and propagated along "rods-of dielectric material whose cross-sectional dimensions aresmall as compared to-the wavelength of said energy.

One of the principal objects of the present invention'is to provide "methods and means for transferring "energy from one dielectric rod to another.

Another-object is to providemethods and means for dividing'the flow of radio frequency energy' betweentwo or'more dielectric guides.

*Afurther "object of the invention is to ,provide amethod 'and means for guiding energy in a l Figure; isuaplan viewof a modification of .the

'device'o'f Figure 1.

"Thin-rods of dielectric material, whenproperly coupled to radio frequency source and utilization elements and excited .in certainumodeahave the property of ,guiding ,rad-io energy .instraight lines with.substantiallynorloss byradiation. .Any 3 discontinuity orurelatively sharp bend in such a rod actsjli-ke .airadiator, and..the energy .tends to continue to propagate .in .the original r direction instead of ..following the rod. 1 have discovered that. energyipropagatingalong aistraightadielec- .tric .rod can be transferred substantially without vloss to another similar .rod,providing thesecond .rod' is near the first-and crosses .itor approaches it substantially at a certain critical angle.

-Referring'to Figure 1, a circular rod VI of di- "electricmaterial such as polystyrene isrcoupled at ione'endtoithe end of a hollow rmetal wave guide "3. The'couplingmay'be'effected simply by making the end of the rod l extendsomewhat within the wave guide 3. to asource, not shown, of high frequency energy. The diameter of the rod l'is'approximately one halfthe'wavelengthin the rod of the energyapplied fto *the g-uide 3. A second dielectric rod *5, slmilaritoithe rod I is disposed as shown-in Fig- The wave guide 3 is coupled ure 1, crossing the rod I'at'an'angle .a. .-A utilization device, fortexample aihorn radiator,i'may be coupled to the end L of therod 5, or theend sur-faceitselfmay be used as'a radiator.

The wave guide '3 may be excited in known manner so that the electric field vector 'isvertical, as indicated by the arrow B in Figure "1. For the purpose of example only, it is assumed that the wavelength of the radio energy is one and one-quarter centimeters, that the rods are polystyrene, and that the diameters of the rods and 5 are one-quarter inch (i. e.0.635 cm. .or about one-half wavelength). Thus'the rod diameter is less'than one wavelength of the energy in the rod.

Whentheangle a between the rods and 5 is about '16 degreesjit is found that substantially all the energy delivered by the wave guide 3 to the rod I is transferred to the rod 5, and appears at the=end'L. Substantially, none o'fthe power arrives-at the end T of the rod I or at the endR of the rod 5. The angle a for maximumpower transfer has been determined experimentally under the above-described conditions to be 15 /2 degrees. With other values of a, the power is divided, some appearing at the point T and some at the point L; but little at the point R:

Relative power at r-oint'T Relative power at a'degrees tpointL This tabulation applies "substantially without change for "all such dielectric rod guides with a 'diamet'er'of about one-half wavelength of the energyof the rod.

The exact reasons for .the above-described phenomena are notknownatpresent. However, lnaccordance with my ,present invention, the effect is applied 'to coupling devices and the like in dielectric rod high 'frequencynetworks.

Referring to Figure 2, two dielectric rods 7 and!) are disposed in spaced parallel relationship; a radio frequency source H (for example, anoscillator') is coupled to one end of "the rod '1, and aload [3, such as a radiatoryis coupled to theremote end o'f the 'ro'd 9. A second'loa'd or-absorbing device ll may -be 'coupled' to the end 7 not cross.

3 of the rod 1. The rods 1 and 9 are separated from each other by sufiicient distance to prevent substantial transfer of energy directly from one to the other. A third rod I is disposed diagonally across the rods 1 and 53, forming an angle a with each, as shown.

The proportions of the output of the source I l which reach the loads I 3 and ll respectively depend upon the angular position of the rod I5. Thus, when a is about 16 degrees, substantially all of the power goes to the load [3. When a. is about 8 degrees, substantially all of the power goes to the load [1. With intermediate values of an the power is divided accordingly. It will be apparent that the device may be used either as a switch or as an adjustable attenuator, as well as a fixed-ratio power dividing device. The structure is also useful for merely transferring power between two offset rods, when loss by radiation is to be minimized.

Figure 3 shows another embodiment of the invention, in which the energy is to be propagated along a relatively sharp curve, or around a corner. In this case, successive rods l9, 2! and 23 are placed with their respective ends crossing as shown. The angle a between successive rods is preferably that required for maximum power transfer from each rod to the next. One intermediate rod, i. e. the rod 2!, is required to go around a bend of about 45 degrees It is evident from the illustration that more rods such as 24 will enable the power to be conveyed through a larger angle, For example, a total of five rods can be used to change the direction of propagation through a right angle.

The foregoing embodiments of the invention have been described as involving crossed rods in contact. However, contact at the points of crossing is not essential, as long as the rods are fairly close to each other at their nearest points. It is not necessary that the rods cross even as skew lines to provide effective transfer of power. Referring to Figure 4, the rod 25 is carrying power in the direction indicated by the arrow. A second rod 21 has one end adjacent the rod 25 and lies at an angle 5 thereto, although the rods do There is a certain critical value of 5 at which substantially all of the power is transferred to the rod 21. The exact value of B depends on the length of the rod 21 and also upon the frequency of the radio energy. The arrangement of Figure 4 may be used as an element of networks like those shown in Figures 2 and 3, in

the same manner as the device of Figure 1 is used.

The invention has been described as a coupling 'or energy transfer device for radio frequency energy, including thin rods of dielectric material with their longitudinal axes crossing. At certain critical angles, substantially complete transfer of energy from one rod to another is achieved. The coupling may be varied by varying the crossing angles, to thereby eifect switching and power division. One or more coupling elements of the described type can be used to convey radio energy in a curved path, or around a sharp bend without substantial radiation loss.

I claim as my invention:

1. In a radio frequency network wherein energy is propagated along relatively thin rods of dielectric material, means for transferring energy from one of said rods to a second lying at a substantial angle thereto, comprising at least one further rod disposed in longitudinal sequence between said first and second rods, each said rod being disposed adjacent to each of its neighbors in said sequence at a critical angle of about 15 to effect substantially unattenuated radio frequency energy transfer therebetween, said rods having a diameter of substantially one-half wavelength in the rod at the operating frequency.

2. In a radio frequency network wherein energy is propagated along at least three relatively thin rods of dielectric material, means for transferring energy from one of said rods to a second lying at a substantial angle thereto, comprising at least one other rod, each said other rod being disposed in longitudinal sequence between said first and second rods, each said rod lying across each of its neighbors in said sequence at an angle of approximately sixteen degrees, said rods each having a diameter of substantially one-half wavelength at the operating frequency at least one of two adjacent rods extending longitudinally a substantial distance in each direction from the point nearest the other rod.

3. A radio frequency network for the transfer of radio frequency energy, including first, second, and third rods of dielectric material having a linear dimension in cross section of approximately one half the wavelength of said energy, means supplying said energy to one end of said first rod whereby said energy is propagated along said rod, and utilization means coupled to one end of said second rod, said third rod being disposed adjacent to both said first and second rods with its longitudinal axis at substantially equal angles to those of said first and second rods at least one of two adjacent rods extending longitudinally a substantial distance in each direction from the point nearest the other rod.

4. A radio frequency network for the transfer of radio frequency energy, including three rods of dielectric material each having a linear dimension in cross section of approximately one half the wavelength of said energy, means to couple a source of radio frequency energy to one end of one said rod whereby said energy is propagated along said rod, and utilization means coupled to one end of a second said rod. and a third said rod lying across both said first and second rods with its longitudinal axis at substantially equal angles to those of said first and second rods at least one of each pair of crossing rods extending a substantial distance longitudinally in both directions from the point nearest the other rod of the pair.

5. A coupling device for radio frequency energy including first and second rods of dielectric material, said rods each having a linear dimension in cross section of the order of one half wavelength of said energy, said second rod being disposed adjacent to said first rod and with its longitudinal axis at an angle with respect to that of said first rod at least one of said rods extending for a substantial distance in both directions along its longitudinal axis beyond the point thereon which is nearest to the other rod, said angle being more than eight degrees and less than sixteen degrees for controlling what portion of said energy is transferred from said one of the rods to the other and what portion continues to be propagated along the former beyond said point. Y

6. A power division network for radio frequency energy, including three rods of dielectric material each having a diameter of approximately one half the wavelength of said energy, means applying said energy to one end of the first said rod forpropagation therealong, said second rod being disposed substantially parallel to said'first rod, and a third rod lying across said first and second rods at least one of each pair of crossing: rods extending a substantial distance longitudinally in both directions from the point nearest the other rod of the pair.

7. A radio frequency system including a source of radio frequency energy, two rods of dielectric material one of which is coupled to said source, said rods each having a linear dimension in cross section of the order of one half wavelength in the rod of the energy of said source, the second rod being adjacent said first mentioned rod, at least one of said rods extending for a substantial distance in both directions along its longitudinal axis beyond the point thereon which is nearest to the other rod, said second rod being disposed with its longitudinal axis at an angle with respect to that of said first rod for controlling what portion it will receive therefrom of the energy which said first rod receives from said source and what portion will continue to be propagated along the first-mentioned rod beyond said point, said angle being more than eight degrees and less than sixteen degrees, and a load coupled to said further rod.

8. A power division network for radio, frequency energy, including a source, three rods of dielectric material having a diameter of approximately one half the wave length of said energy, means for coupling one of said rods to said source for applying said energy to one end of said one rod for propagation therealong, the second rod being substantially parallel to said first rod, and the third said rod lying across said first and second rods, and loads coupled to said first and second rods at least one of each pair of crossing rods extending a substantial distance longitudinally in both directions from the point nearest the other rod of the pair.

9. In a radio frequency network including relatively thin rods of dielectric material each having a diameter of substantially one-half wavelength in the rod at the operating frequency and means applying energy to one end of one of said rods for propagation along said rod, means for transferring said, energy from said one rod to a last said rod lying at a substantial angle thereto, comprising a plurality of further said dielectric rods in sequence between said first and last, each rod crossing a preceding one of said rods at an angle of approximately sixteen degrees at least one of each pair of crossing rods extending a substantial distance longitudinally in both directions from the point nearest the other rod of the pair.

'10. Dielectric means for guiding radio frequency energy around a corner comprising a plurality of dielectric rods disposed in longitudinal sequence with each two sequentially occurring rods mounted in fixed angular relationship and crossing each other for controlling what portion of said energy is transferred from one of said two rods to the other and what portion continues to be propagated along the former, and with said one of the two rods extending for a substantial distance in both directions along its longitudinal axis beyond the point thereof nearest to the other, said rods having a diameter of one-half wavelength in the dielectric at the operating frequency at least one of each pair of crossing rods extending a substantial distance longitudinally in both directions from the point nearest the other rod of the pair.

11. In a radio frequency network, an arrangement comprising two long relatively thin rods of dielectric material, and means to couple radio frequency energy to one of said rods to be guided thereby, one of said rods being closely adjacent to and crossing the other at an inclined angle, at least one of said rods extending for a substantial distance in both directions along its longitudinal axis beyond the point thereon which is nearest to the other rod, said rods each having cross-sectional linear dimensions less than a wavelength of the energy in the dielectric material at the operating frequency, whereby a portion of said radio frequency energy is transferred from one rod to the other.

12. An arrangement as claimed in claim 11, said rods being movable to vary the angle of inclination therebetween to change the proportion of energy transmitted from one to the other.

HARLEY IAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,129,712 Southworth Sept. 13, 1938 2,142,138 Llewellyn Jan. 3, 1939 2,196,166 Bryce Apr. 2, 1940 2,449,182 Sontheimer Sept. 14, 1948 OTHER REFERENCES Principles of Radar, published by McGraw Hill, New York, 1946, pages 10-1 and '10-32. 

